Annuloplasty rings to repair cardiac valves have been used mostly for mitral and tricuspid valve repairs. Such rings are implanted within the heart chambers and are as such in direct contact with patient's blood flow.
Many designs of annuloplasty rings have evolved over the years. Some rings are completely closed while others are partially closed. Two schools of thought still persist: one school advocates a rigid ring is best to resize the mitral or tricuspid valve annulus, while a second school believes it is best to resize the annulus with a non-rigid or flexible ring. The latter rings, although being non-rigid or flexible, are however generally not elastic and are as such not expandable as a function of the varying cardiac cycle parameters and associated ventricular mechanics. The latter rings passively comply to the desired shape in which the surgeon implants them during the surgical repair procedure, or if they are flexible may flex passively during the varying phases of the cardiac cycle.
Annuloplasty rings for the aortic valve are currently not commercially available and generally not used. Some aortic annuloplasty ring concepts placed internally to the aortic root, in the vicinity of aortic leaflets, have been tried with little or no success in correcting aortic insufficiency. This may be due to a number of reasons including the relatively more complex anatomy of the aortic valve annulus which is coronet shaped (unlike the mitral and tricuspid annuli which are generally planar), and the dynamics of the aortic root which expands considerably between the diastolic and systolic phase in the cardiac cycle.
Consequently, current aortic valve surgery is mostly dominated by valve replacement procedures. More specifically, in treating aortic valve insufficiencies due to an increasingly widespread range of pathological conditions (including Marfan disease, aortic annulo-ectasia, idiopathic root dilations, bicuspid valve disease with associated aneurysm, and acute aortic dissection), very few aortic valve repair procedures are practised to restore competence to the native aortic valve while preserving native leaflets. This is largely due to the technically demanding nature of current valve repair or sparing procedures such as the most common “David Reimplantation” or “Yacoub Remodelling”. Moreover, due to the lack of a standardized technique that would advantageously rely on enabling apparatus and cardiac prosthesis specifically designed to facilitate the aortic valve sparing procedure with a physiologically representative reconstruction, current surgical interventions are sometimes characterized by surgeon-dependent outcomes. Due to this lack of specially designed prosthesis and apparatus, practicing surgeons must often resort to “off-label use” of existing implant materials to tailor a surgical solution during the surgical intervention.
Due to the above drawbacks, even though a patient suffering from a dilated aortic root may have viable valve leaflets, currently in the great majority of cases, the native valve and aortic root are removed and are replaced by a valved synthetic conduit in a procedure known as the “Bentall” procedure. As a result, the patient's leaflets are not preserved but are instead replaced by a prosthetic mechanical valve, and the patient's dilated aortic root is not resized but removed and replaced by synthetic conduit such as Dacron or ePTFE. One of the main drawbacks of the Bentall procedure is that the patient is placed on long-term anticoagulation therapy in Bentall procedures using mechanical valves, and a risk of valve degradation and need for re-operation in Bentall procedures using a bioprosthetic valve.
In recent years, the scientific literature reflects a significant effort In the medical research community directed not only to an understanding of the functional anatomy or physiology of the aortic valve and root complex, but to the development of surgical repair techniques that are able to preserve viable native leaflets while correcting aortic insufficiency. Such surgical repair techniques are commonly referred to as “valve-sparing surgeries”.
The valve sparing surgery commonly known as “David Reimplantation” involves the placement of a Dacron root prosthesis or synthetic aortic conduit over the scalloped native tissue, where it is sutured both below the valve leaflets through the valve annulus, and above the valve leaflets. The procedure is generally long and difficult to perform, and often results in leaflet impact or concussion with the walls of the Dacron prosthesis during the ejection phase of the cardiac cycle. In addition, the absence of radial compliance of the Dacron root prosthesis does not allow for an increase in diameter at the sinotubular junction STJ during ejection, which is an important aspect in providing optimal blood transport while preserving valve dynamics and valve leaflet durability. As such, the normal valve physiology is compromised in this valve-sparing intervention.
The second type of valve sparing operation, commonly known as “Yacoub Remodelling”, involves scalloping the Dacron root prosthesis to essentially match the remaining native tissue, and using a running suture to attach the prosthesis to the native aortic root tissue. Although this method addresses some of the problems of the reimplantation method, it does not directly constrain the valve annulus diameter, which has been seen to result in annular dilatation over time. As such, this procedure is not well suited for resizing a dilated valve annulus, and may be limited to replacing aneurysmal aortic tissue. Since it also relies on a Dacron vascular conduit, which is radially non-expansible, the expansion of the aortic root at level of commissures, in the plane joining the commissures or scalloped peaks of native tissue, tends to be constrained by the conduit fabric hoop. As such, the leaflet free edges are hindered in assuming their triangulated relationship, since the plane containing the sinotubular junction (STJ) is generally not expansible in this surgical procedure. Unlike the reimplantation procedure, however, the leaflets have a lower likelihood of hitting the conduit wall since pseudo-sinuses may be fashioned from a scalloped Dacron conduit to recreate the pouch-like configuration seen in a healthy aortic root. Nonetheless, in the remodelling valve-sparing intervention, the normal native valve physiology is compromised, and the effectiveness of resizing a dilated aortic annulus, or preventing its future dilatation, with a scalloped vascular conduit remains questionable.
Although useful and widely accepted for some aortic reconstruction procedures, conventional valve-sparing procedures and devices nevertheless suffer from numerous drawbacks or shortcomings that are manifested and become apparent both during the operative and post-operative periods.
Accordingly, there exists a need for an improved aortic root reconstruction procedure, and enabling devices, that allows correction of a dilated aortic annulus (with associated replacement of aneurysmal aortic tissue when applicable), while preserving the native leaflets and maintaining normal valve physiology. Typical prior art devices and methods for aortic reconstruction or valve sparing interventions do not offer a dynamic device configuration that may advantageously vary during the different phases of the cardiac cycle, and consequently restore or preserve normal aortic valve physiology. More specifically, there exists a need for such an expandable annuloplasty ring which, when implanted, dynamically controls the valve annulus at the level of the aortic root where it is implanted. Such an expandable annuloplasty ring would provide the many benefits including: resizing of a dilated aortic root or annulus in a physiologically representative manner, restoring native leaflet coaption and valve competence during diastolic phase of cardiac cycle, improved blood flow through the open aortic valve during the systolic phase of the cardiac cycle, minimized stresses on native leaflets as they are cycled from their diastolic to systolic configuration. Also beneficial would be a procedure with reduced time and difficulty relative to current valve sparing procedures.
Cardiac valve prostheses are generally mounted on a holder assembly to facilitate their manipulation during the course of a surgical intervention and their implantation. Current holder assemblies are characterized by a number of drawbacks.
A great majority of holders are configured with a rigid handle and a fixed orientation of the holder body or prosthesis carrier relative to the handle. Such a mechanical limitation does not allow the surgeon to orient the holder body relative to the handle in order to optimize the delivery of the prosthesis to the implant site. Some holder assemblies have been configured with malleable handles in an attempt to alleviate this drawback. However, such malleable handles are generally difficult to reshape in different bent configurations once they have been initially bent. Moreover, the material of such malleable handles work hardens with repeat bending making it progressively more difficult to easily bend such handles. As a result, some holder assemblies have introduced shape memory alloys, such as Nitinol, for the material of the handle. Handles made from Nitinol that would be bent during the surgical procedure would resume their straight unbent shape after being exposed to sterilization temperatures. Some of the drawbacks associated with Nitinol handles include cost, and generally insufficient stiffness of such handles given the highly elastic properties of Nitinol. In order to make Nitinol handles malleable and easy to bend into the desired shape by the surgeon, such Nitinol handles are equally easy to bend out of desired shape when the cardiac prosthesis mounted on end of such handles is exposed to tissue or suture loads during the surgical intervention.
A great number of holder assemblies are configured with a threaded interface between the handle and the prosthesis carrier or holder. Such threaded interfaces do not provide the ability to orient the holder body relative to the handle. As well, such threaded interfaces generally do not provide ability for rapid changeover of prosthesis holders or sizers, since unthreading and rethreading is a relatively lengthy process with inherent risks of cross-threading. Current alternatives to threaded interfaces, such as quarter turn bayonet arrangements, are also currently used but also do not offer the ability to orient the holder body relative to the handle. Such bayonet arrangements are relatively large in size thereby creating greater obstruction to the surgeon view of the surgical site. Such obstruction is particularly problematic when the surgeon is visually assessing the suitability of a selected size of prosthesis. Also, bayonet arrangements are generally more difficult to clean and sterilize given the design of cooperating bayonet features such as blind holes and elongated slots and dogs.
Another current technique for coupling the handle to the holder or prosthesis carrier consists of a tapered distal tip on the handle which is pressed into a similar cooperating tapered opening in the holder. This provides a friction fit which may be separated by applying a separation force between the holder and the handle. This technique does not provide a positive lock between the handle and holder (or sizer) and the engagement forces may vary due to dimensional tolerances and wear at such interfaces. Moreover, it may be difficult to remove the holder from the handle when the holder is placed adjacent to the native valve during the surgical intervention, due to the variability in frictional engagement and since the separating force must be applied to the holder in the chest cavity while the handle is pulled away from the holder away from the chest cavity. Alternatively, the friction fit may be too loose resulting in holder (or sizer) easily disengaging from the handle making for an unsecure assembly. Other types of holder to handle interfaces rely on similar distal disengagement features whereby if the need to detach the handle from holder arises during the surgical procedure, the surgeon generally needs to get inside the chest cavity to separate the holder form the handle.
Due to the current lack of suitable mechanical interfaces to allow rapid changeover between different sizers and a common handle, and a secure engagement during the sizing intervention, current sizers are each integrally mounted to there own separate handle.
Accordingly, there exists a need for a holder assembly that resolves the drawbacks associated with current holders. More specifically, there is a need for a holder assembly that allows rapid quick changeovers. There is a need for holder assembly that allows the holder or prosthesis carrier to be variably mounted in a number of secure orientations relative to handle so that the optimum mounting arrangement can be selected to suit the specific anatomy of the patient, the specific anatomic routing of the surgical approach, or the surgeon work preference.
In accordance with the aortic annuloplasty ring of the present invention there exists the need for a specially designed holder assembly to mount an elastic or expansible annuloplasty ring in a mounting configuration that is similar to a physiologic configuration that it will be exposed to in-vivo, such as physiologic configuration being different to the free state configuration of the ring. Such a holder will allow the surgeon to assess the suitability of a ring size while the ring is held in an in-vivo configuration prior to removing the elastic ring from its holder, and allowing it to resume its free state configuration.